FR2518657A1 - CLOSING PISTON FOR FIXED CYLINDER PUMP - Google Patents

Abstract

VARIABLE VOLUME PUMP FOR HYDRAULIC SYSTEM, DESIGNED TO LIMIT THE FLUID FLOW WHEN THE HYDRAULIC SYSTEM DOES NOT REQUIRE THE ENTIRE VOLUME OF FLUID DELIVERED BY THE PUMP. THE PUMP INCLUDES ONE OR MORE ROWS OF PUMPING PISTONS 14 WITH ALTERNATIVE MOVEMENT ARRANGED RADIALLY AROUND A CRANKSHAFT 16. THE ROTATION OF THE CRANKSHAFT RESULTS IN THE CENTRIFUGAL FLOW OF FLUID THROUGH OPENINGS 26 PROVIDED IN WHICH TRUNKS 18, FILLING THE PUMPING PISTONS. EACH PUMPING PISTON, ON REVERSE OF ITS MOVEMENT IN A PUMPING CHAMBER, CAUSES THE DISCHARGE OF THE FLUID IT CONTAINS TOWARDS THE HYDRAULIC SYSTEM THROUGH A DISCHARGE PORT 40. A SHUT-OFF PISTON 42 IS PROVIDED TO L 'INSIDE THE PUMPING CHAMBER 44 FACING THE PUMPING PISTON AND SPACE THEREOF. THE CLOSURE PISTON IS NORMALLY IN PRESSURE AGAINST A 52 SEAT WHEN THE VALUE OF THE PRESSURE IN THE HYDRAULIC SYSTEM IS LESS THAN THE VALUE FOR A REDUCTION OF FLOW. WHEN THE SAID PRESSURE REACHES A PREDETERMINED VALUE, A COMPENSATING PRESSURE IS APPLIED TO THE CLOSURE PISTON AND MOVES IT TO THE PUMP PISTON.

Description

The present invention relates to improvements

  tions to fixed displacement pumps intended to meet the requirements inherent in a hydraulic system while requiring lower power in operation under low load, and more particularly a pump which prevents the flow of fluid when the hydraulic system does not require

  the entire volume of fluid delivered by the pump.

  We already know earthmoving machines

  such as backhoe loaders or backhoes

  ses which comprise a bucket or shovel mounted on a tractor and intended to be raised or lowered, tilted, or otherwise brought to a defined height by means of a mechanism suitable for a certain type of work to be carried out Such displacements of the bucket or shovel

  are carried out in a conventional manner by cylinders

  dres-hydraulics supplied by a pressurized fluid

supplied by a suitable pump.

  A classic operation in terms of terraces-

  The penetration of a bucket or a shovel into a pile of material Hydraulic systems intended for such an application require a large volume of fluid at low pressure, this in order to allow rapid displacement of the connecting rods, and therefore) bucket or shovel, during its effort Then a small volume of high pressure fluid must be available to ensure the tilting of the bucket or shovel necessary for it to detach part of the material from the pile or to lift the material in the

bucket or shovel.

  A known solution consists in providing a

  fixed displacement feed pump for supplying

  set the required amount of pressurized fluid, excess

  of fluid being discharged through a relief valve

  It is also known to use the engine of the -

  tractor to drive the pump and the pump then generally continuously delivers its maximum quantity of fluid because the engine speed of the tractor is constant Most of the time, this maximum volume of fluid is not required and the power supplied negated by excess fluid must then be absorbed by the system in the form of a heating

  undesirable and wear of the relief valve.

  Another solution known from the prior art consists in using a variable displacement pump with automatic control, so that the flow rate of the pump can be kept at a minimum value except when a higher flow rate is required by the system. in this way requires less power to supply the hydraulic system, decreases the heating of the fluid during the operation under low load, allows a possible undersizing of an oil radiator and reduces the noise generated.

  by the pump and the relief valve during the operation

ration under low load.

  A major drawback inherent in the use of a variable displacement pump is its cost A

  variable displacement pump is significantly more expensive

  reuse than a comparable fixed displacement pump, which increases the overall cost of manufacturing earthmoving machines such as backhoe tractors or backhoes Thus the present invention aims to advantageously provide an improved fixed displacement pump which is capable of reduce the volume of excess fluid during operation under low load, its operation requiring

  thus lower power and lower cost

  ble than that of a variable displacement pump compared

  saddle. The variable volume pump according to the present invention can be used in equipment

  conventional earthmoving equipment, including

  loader shovelers and backhoes La

  pump is intended to meet the requirements of ali-

  ment of a hydraulic system as used in backhoe tractors or

  backhoes, in which a large volume of fluid

  as long at low pressure is first of all required for the rapid attack of the material, then a small volume of fluid at high pressure allows the clamping of the jaws, the loading or the packing Of course, the pump according to the present invention can be used in all areas o D such

constraints are met -

  A hydraulic system equipped with the pump according to the present invention operates by consuming less energy and allows less heating.

  of the fluid during its operation under low load.

  The hydraulic pump according to the present invention

  tion includes a frame housing one or more ranch-

  reciprocating pumping pistons,

  arranged radially around a crankshaft The vi-

  the lebrequin is substantially hollow and has a plura-

  lity of cam bosses or trunnions Each piston

  pump is mounted on the journal which corresponds to it

  lays by means of a free-moving shoe A wider spherical end part, or head, traversed by an axial bore, allows fluid to flow through the piston head and fill

this one.

  The hydraulic fluid supplies the interior of the

  crankshaft through a conduit The rotation of the crankshaft

  brequin results in the centrifugal flow of

  fluid through openings provided in the barrels

  lons, which causes the filling of the pumping pistons.

  During the reversal of the movement of each pumping piston, pressurized fluid is discharged to a conventional hydraulic circuit as used in an earth-moving machine. Each pumping piston has a tubular part cy-

  lindrique mobile inside a pumping chamber

  ge When the movement of the pumping piston is reversed, the volume of fluid filling the part '

  tubular is brought against a shut-off valve

  as the fluid pressure in the tubular part exceeds the load threshold of the shut-off valve, the latter loosens from its seat and thus allows

  the delivery of fluid to the hydraulic system.

  A sealing piston is provided in the chamber

  pumping device and arranged opposite the pumping piston.

  The sealing piston includes a tubular part

  cylindrical arranged to slide in a sleeve.

  A spring is mounted inside the part

  tubular in abutment against a seat of the shut-off piston

  ration, and pushes the closing piston towards the pumping piston The lower end of the closing piston acts as a stop for a return spring mounted inside the tubular part of the pumping piston and intended to maintain the piston

  pump in position on its shoe The piston-shutter

  ration is normally pressed against its seat when the value of the pressure in the hydraulic system is lower than the value imposing a

  reduction in flow rate So all of the fluid

  placed by the pumping piston passes through an orifice

  to supply the hydraulic system -

  as desired, until the pressure

  in the hydraulic system reaches a pre-

  determined corresponding to the need to reduce the

  flow from the pumping piston When the pressure

  sion in the hydraulic system reaches this predetermined value, fluid, at a certain compensation pressure, is brought to the part

  tube of the sealing piston, which has the

  sequence the detachment of the sealing piston

  its seat as well as the compression by the obturating piston

  ration of the pumping piston return spring.

  For the maximum pressure required in the system, the shut-off piston comes to stick to the piston

  pumping system and follows it during its vacuum stroke

  ration to thereby interrupt the flow of fluid through the discharge port Thus the flow of

  fluid in the discharge port decreases in proportion

  increasing the pressure in the system until a maximum required outlet pressure is obtained for a minimum flow of fluid. The fluid pressure in the hydraulic system can be

  used to control the position of the shut-off piston

  tion in the pumping chamber, in order to reduce the

  fluid flow to the hydraulic system

  The object of the present invention is also to provide auxiliary devices for generating the control signal necessary for positioning the

  shut-off piston, including central regulators

  trifuge or speed control mechanisms.

  Other advantages of the volume pump

  variable according to the present invention will be better com-

  taken from reading the following description of a

  preferred embodiment, made with reference to the accompanying drawings, in which:

  Figure 1 shows an elevational view

  tion of the variable volume pump, partially cut off for easier viewing, Figure 2 shows an enlarged view of the

  pump piston mechanism, the shut-off piston

  tion being in abutment against its seat, and Figure 3 shows an enlarged view of the pump piston mechanism, the shutter piston being attached to the pumping piston. Referring to Figures 1 to 3, a hydraulic pump 10 includes a frame 12 housing one or more rows of movement pumping pistons

  alternative 14 arranged radially around a city

  brequin 16 The crankshaft 16 is substantially hollow and has a plurality of cam bosses or trunnions 18 Each pumping piston 14 is mounted on the trunnion which corresponds to it by means of a free-moving pad 20 A wider spherical end part or head 22, traversed by an axial bore 23, allows fluid to flow

  through the piston head and fill it.

  The hydraulic fluid is brought inside the crankshaft 16 through a conduit 24 The rotation

  -20 of crankshaft 16 results in central flow

  fluid leakage through openings 26-pre-

  seen in the trunnions, which causes the filling of the pumping pistons 14 When the movement of each piston 14 is reversed, pressurized fluid is discharged towards a conventional hydraulic circuit (not shown) as used in an earthmoving machine . Each pumping piston 14 has a

  cylindrical tubular part 28 arranged for sliding

  inside a sleeve 30 When the piston

  14 moves upward from its re- posed position

  shown in Figure 2, the volume of fluid filled

  sant the tubular part 28 is brought through an opening 32 provided in a seat 34 against a stop valve 36 When the fluid pressure in the tubular part 28 exceeds the reaction exerted by a spring 38, then the stop valve 36 peels off from its seat 34 and thus allows the fluid to exit to the hydraulic system, through a discharge orifice 40. A closing piston 42 is provided in the pumping chamber 44 and disposed opposite the pumping piston 14 The piston shutter 42 includes

  a cylindrical tubular part 46 arranged for coupling

  smooth in a sleeve 48 A spring 50 is mounted inside the tubular part 46 in abutment against a shutter piston seat 52, and pushes the shutter piston 42 towards the pumping piston 14 The lower end 53 the closing piston 42 acts as a stop for a return spring 54 mounted inside the tubular part

  28 of the pumping piston and intended to maintain the piston

  your 14 in position on its pad 20.

  The shut-off piston 42 is normally in abutment against its seat 52 when the value of the pressure in the hydraulic system is lower than the value imposing a reduction in flow. Thus all the fluid displaced by the pumping piston 14 passes through. the discharge port 40 to supply the hydraulic system in the desired manner, until the pressure in the hydraulic system reaches a predetermined value corresponding to the need to reduce the flow from the piston of

  pumping 14 When the pressure in the hydrau-

  lique reaches this predetermined value, then the par-

  tubular tie 46 is subjected to a compensating pressure

  tion via an inlet port 58 and an opening 60 provided in the seat 52 of the shutter piston, which results in the detachment of the shutter piston 42 from its seat and compression by the closing piston 42 of the spring 54 of the pumping piston For a maximum pressure required in the system, the closing piston 42 comes to stick to the pumping piston 14, as shown in FIG. 3, and follows the piston of pumping 14 during its suction stroke so as to interrupt the flow of the fluid through the discharge port 40 Thus the flow of fluid at the outlet of the discharge port

  decreases in proportion to the increase in the

  pressure in the system until obtaining, for a

  minimum fluid flow, maximum outlet pressure

male required.

  Inlet port 58 can be connected to the system

  hydraulic for intake pressure compensation

  necessary to control the shutter piston

  tion 42 Thus the fluid pressure in the hydraulic system can be used to control the position of the shut-off piston 42 in the pumping chamber 44 The present invention also has for

  purpose of providing auxiliary devices for

  generate the command signal required for the position-

  closure piston 42, comprising centrifugal regulators or control mechanisms

of speed.

  Of course, the above description is

  given by way of nonlimiting example, the scope of

  the invention extending to the content of the claims

attached.

18657

Claims (2)

RWVENDICATIONS   1 Variable volume pump for supplying fluid to a hydraulic system, designed to limit the flow of fluid when the system does not require the entire volume of fluid delivered by the pump, said pump comprising at least one piston of reciprocating pumping (14), said pumping piston comprising a tubular part movable in a pumping chamber, means for filling the tubular part of the pumping piston using   fluid during a suction stroke of said pis-   pumping tone, means for discharging the fluid contained in said tubular portion of the pumping piston through a discharge port (40) to said hydraulic system when the fluid pressure in said hydraulic system is lower than the fluid pressure in said tubular part of the pumping piston, characterized in that it   further comprises a closure piston (42) available   dried inside said pumping chamber (44) facing said pumping piston (14), said piston   obturation comprising a normal tubular part-   ment in abutment against a sealing piston seat when the value of the pressure in said hydraulic system is lower than the value imposing a reduction in the flow of fluid, means for bringing -X   the interior of said tubular part of the piston   turation of the fluid under a compensating pressure   intended to cause detachment of the sealing piston   tion of its seat when the pressure in said system   hydraulic reaches a predetermined value, said pis-   the shutter tone being movable towards said pumping piston to follow said pumping piston during its suction stroke when the pressure in said   hydraulic system reaches said predetermined value-   mined, the sealing piston limiting or interrupting   thus panting the flow of fluid at the outlet of said orifice discharge (40).   2 variable volume pump according to claim 1, which further comprises elastic means disposed inside said tubular part of the pumping piston and arranged to bear on   one end of said sealing piston.